1. Field of the Invention
This invention relates generally to fluid handling and more particularly to hinged type liquid valve seals.
2. Description of the Prior Art
Generally, waste accumulated during aircraft passenger flights is held in a collecting tank until, after landing, airport facilities are used to drain the waste from the tanks. To drain the waste, a port is provided in a convenient location in the aircraft fuselage. A removable plug is inserted into the drain port for maintaining the waste in the tank. Prior to draining the tank, the plug is removed.
In order to achieve plug removal, a bi-conduit valve and plug assembly was devised. In this prior art arrangement the valve was fitted to the port and a key was used to remove and retract the plug into one of the conduits while the waste was drained through the other conduit of the valve. While this arrangement is generally satisfactory, the plug has presented some problems.
The plug of the prior art is generally annular including a radially expandable resilient sealing member. With little tolerance between the annular inner periphery of the port prior to expansion, only slight radial expansion of the resilient member is required to urge the outer annular periphery of the resilient member into sealing engagement within the port.
One problem associated with such plugs has involved certain difficulty experienced by ground crew personnel in reinserting the plug into the port after the tank is drained. The plug will sometimes "hang-up" on the port sidewall so as to make plug reentry into the port difficult. Also, should the plug be misaligned in the port, it is still possible to actuate the plug locking mechanism so that in effect the ground crewman thinks the plug is properly seated and locked in the port when, in fact, the plug is misaligned in the port and the locking mechanism may become jammed.
As a result, a leak may occur during high altitude flight due to the pressure differential across the misalinegd plug. Leaking fluid can freeze at high altitude resulting in a hazardous ice formation on the aircraft in the vicinity of the port.
It would be advantageous to have a novel seal for the port which avoids the common problems associated with the prior art plugs.